The present invention relates generally to methods and apparatus for determining the cut resistance of materials, and more particularly to a method and apparatus for determining the cut resistance of a film or sheet.
The use of disposable cutting boards or surfaces for preparation of food or other articles is well known. Depending on the use of the cutting boards or surfaces, a specific cut resistance may be necessary. In such cases, testing must be performed in order to produce a product with the necessary cut resistance. Several testing methods have been developed for measuring the cut resistance of materials.
ASTM Test Method F 1790-97 entitled xe2x80x9cStandard Test Method for Measuring Cut Resistance of Materials Used in Protective Clothingxe2x80x9d discloses a method and apparatus for measuring the cut resistance of various protective materials. The test instrumentation includes a cutting blade mounted on a motor-driven balanced arm. A known load is applied to the arm and brought into contact with a specimen mounted on a mandrel. The arm is moved relative to the specimen and the distance that the arm moves relative to the specimen until the point at which cut-through of the specimen occurs is measured. This process is repeated for several different loads and the resulting force-distance data is used to determine various tensile properties of the material. Because the cutting blade only stays in contact with a highly localized point of a specimen during the test, the method and apparatus are only suitable for measuring the cut resistance of homogeneous products.
ASTM Test Method D 3822-01 entitled xe2x80x9cStandard Test Method for Tensile Properties of Single Textile Fibersxe2x80x9d discloses a test method for measuring the tensile properties of man-made single textile fibers. A single-fiber specimen of sufficient length to permit mounting in a tensile machine is placed under increasing tensile forces until breakage of the fiber occurs. Various tensile properties are calculated from the test results.
Boone U.S. Pat. No. 4,864,852 discloses a method and apparatus for measuring the cut-resistance of flexible materials such as films, fabrics, felts, and papers. The apparatus includes a material wrapped around a mandrel that is rotating at a predetermined speed and a cutting edge that repeatedly falls on the material covering the mandrel. The cutting edge falls in the same spot and with the same force until it cuts through the material and makes electrical contact with the mandrel. The number of times that the cutting edge contacts the material until the edge contacts the mandrel is noted and used as a measure of the relative cut resistance of the material.
Nishiyama et al. U.S. Pat. No. 4,934,185 discloses a device for measuring the adhesive strength and shear strength of coated films. The device includes a cutting blade placed under a certain load and at a certain rake angle, wherein the load causes the blade to move in a vertical direction to penetrate the surface of the coated film and the load and rake angle cause the blade to slice the coating on the film. A cutting force of the blade is measured by a pressure detector and a vertical displacement of the blade is measured by a differential transducer, and the resulting data are used by a personal computer to calculate the adhesive strength and shear strength of the coated film.
Otten et al. U.S. Pat. No. 6,274,232 discloses an absorbent sheet material and an apparatus for testing the slice resistance thereof. The apparatus includes a knife blade disposed in a knife holder and a sample mounted on a platform and disposed below the knife holder. A known load is applied to the knife blade in the vertical direction and the platform is moved under the weight of the knife blade. A series of slices under increasing load are made until the knife cuts through the sample and slice resistance is calculated as the slice force per sample thickness.
According to one aspect of the present invention, a device for determining the cut resistance of a sample includes a blade wherein the blade and the sample are relatively movable and a first apparatus that transfers energy to at least one of the sample and the blade to cause relative movement thereof in a direction parallel to a surface of the sample such that the blade contacts and cuts the sample until the imparted energy is expended and relative movement is terminated. A second apparatus measures a parameter of the relative movement to obtain an indication of the cut resistance of the sample.
According to a further aspect of the present invention, a device for determining cut resistance of a material includes a sample holder having a known mass wherein the sample holder is adapted to receive a sample of the material and a blade. Guide apparatus is provided for effecting relative movement of the sample holder and the blade holder under the influence of gravity along a path from a particular initial position wherein the material sample is out of contact with the blade and a final position wherein the material sample is in stationary contact with the blade thereby forming a cut having a cut length in the sample. Measurement apparatus is also provided for indicating a length of the path, the path length and the cut length being used to obtain an indication of cut resistance.
According to yet another aspect of the present invention, a method of determining a cut resistance of a material comprises the steps of providing a sample of the material and a blade wherein the sample and the blade are relatively movable and imparting energy to at least one of the sample and the blade to cause relative movement thereof in a direction parallel to a surface of the sample such that the blade contacts and cuts the sample until the imparted energy is expended and relative movement is terminated. A parameter of the relative movement is measured to obtain an indication of the cut resistance of the sample.
According to a still further aspect of the present invention, a method of determining a cut resistance of a material includes the steps of providing a movable sample holder having a known mass wherein the sample holder is adapted to receive a sample of the material and providing a stationary blade holder and a blade mounted to the blade holder. The movable sample holder is positioned at a predetermined height above the blade. The movable sample holder is released to cause the sample holder to move under the influence of gravity until the sample contacts the blade and is cut thereby for a cut distance until movement of the sample holder is terminated. The cut distance and the predetermined height are used to obtain an indication of the cut resistance of the sample.
According to yet another aspect of the present invention, According to yet another aspect of the present invention, a method of determining cut resistance inhomogeneity of a material includes the steps of providing a sample of the material and a blade wherein the sample and the blade are relatively movable and imparting energy to at least one of the sample and the blade to cause relative movement thereof in a direction parallel to a surface of the sample such that the blade contacts and cuts the sample until the imparted energy is expended and relative movement is terminated. The position of at least one of the sample and the blade is measured to obtain an indication of the local inhomogeneity of cut resistance of the sample.
Other aspects and advantages of the present invention will become apparent upon consideration of the following detailed description.